GNU gdb (GDB) 7.3.1 Copyright (C) 2011 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "i686-pc-linux-gnu". For bug reporting instructions, please see: <https://www.gnu.org/software/gdb/bugs/>... Reading symbols from /tmp/gdb/example...done. (gdb) run Starting program: /tmp/gdb/example Program received signal SIGSEGV, Segmentation fault. 0xb7ee94f3 in strlen () from /lib/i686/cmov/libc.so.6 (gdb) bt #00xb7ee94f3instrlen()from/lib/i686/cmov/libc.so.6 #10x08048435infoo_len(s=0x0)atexample.c:7 #20x0804845ainmain(argc=<optimizedout>,argv=<optimizedout>)atexample.c:14